Growth regulation of a human mature B cell line, B104, by anti-IgM and anti-IgD antibodies.

An EBNA- human B lymphoma cell line, B104, was established. B104 cells express IgD as well as IgM on their surface, which is thought to be a basic characteristic of mature B cells. The growth of B104 cells was inhibited by treatment with a panel of anti-IgM antibodies. Cell cycle analyses revealed that the transition of B104 cells from the G2/M to the G0/G1 phase of the cell cycle was markedly inhibited by treatment with anti-IgM antibodies. Progression of B104 cells to the M phase of the cell cycle was found to be suppressed in the presence of anti-IgM antibodies. In contrast, both the entrance of G0/G1 phase cells into the S phase and the progression of S phase cells to the G2/M phase of the cell cycle did not seem to be inhibited significantly by treatment with anti-IgM antibodies. These results indicate that the mechanism of the inhibition of growth of B104 cells by anti-IgM antibodies is blockage of the transition from the G2 to the M phase of the cell cycle. In contrast to anti-IgM antibodies, anti-IgD antibodies could not cause growth inhibition of B104 cells at all. B cell growth factors such as IL-4 and IL-6 had no effect on the inhibition of growth of B104 cells by anti-IgM antibody. IFN-alpha and -beta, which have no B cell growth factor activity, did increase the number of cells that survived the treatment with anti-IgM antibodies. B104 is an excellent experimental model for the study of the mechanism of signal transduction through sIg as well as the functional difference between sIgM and sIgD.